30.13.3.2 Logic Scan Time
The logic time includes the logic features and display and the
display features (screen display, touch panel processing,
communication). The logic feature runs the logic programs. There
are two scan modes for the display unit; a fixed scan time mode and
a CPU scan percentage mode.
Fixed Scan
This mode maintains the specified scan time.
It allows you to process a logic program in a certain cycle. It
is suitable for programs that prioritize control (logic programs)
and for which the screen is mainly used for monitoring (data
display) with few operations required.
Display Processing Time = Setting Value for
Fixed Scan Time (ms) - Logic Time
For example, if 50 ms is specified for the fixed scan time, and
the logic executing time is 20 ms,
Display Processing Time = 50 ms - 20 ms = 30
ms
As the logic time becomes longer, the processing time becomes
shorter. For this reason, the display update speed on the display
unit becomes slower; however, the logic program runs
continuously.
-
The minimum scan time setting is 10 ms.
-
For the scan setting, input 10 ms or larger
by 1 ms increments.
-
The scan time is automatically adjusted when
the relationship between the logic time and fixed scan time is as
follows.
|
Model
|
Conditions when the Scan Time is
automatically adjusted
|
Examples of the Automatic Adjustment of Scan
Time
|
|
GP-3300 Series
LT3000 Series
|
When the Logic Time exceeds the Fixed Scan Time
of 30%, the scan time is adjusted to "Logic Time divided by
0.3".
|
-
Fixed Scan Time: 50 ms
-
Logic time: 30 ms
Scan time is adjusted to 100 milliseconds.
|
|
GP-3400 Series
GP-3500 Series
GP-3600 Series
GP-3700 Series
|
When the Logic Time exceeds the Fixed Scan Time
of 50%, the scan time is adjusted to "Logic Time divided by
0.5".
|
-
Fixed Scan Time: 50 ms
-
Logic time: 30 ms
Scan time is adjusted to 60 milliseconds.
|
CPU
Percentage Scan
This mode specifies the logic time occupancy (%) during scan
time and changes the scan time for operation.
The mode prevents pressure on the display processing time caused
by increased logic time, and it is suitable for systems that
prioritize speed in screen operations and screen switching.
Scan Time = Logic Time / Setting Value for
the CPU Scan Percentage (%)
For example, if 40% is specified for the CPU scan percentage and
the logic executing time is 20 ms:
Scan Time = (20 / 40) x 100 = 50 ms
Display Processing Time = 50 ms - 20 ms = 30
ms
As the logic time becomes longer, the display processing time
and the scan time become longer. For this reason, as the logic time
becomes longer, the time allocated for the display processing
becomes longer. This results in improved display update speed on
the display unit while slowing down the processing cycle of the
logic programs.
-
Specify the scan time value for the CPU scan
percentage by 1 ms increments.
-
The processing time per instruction in the
logic program remains unchanged.
-
You cannot specify a CPU scan percentage
larger than 50%.
-
If 50% is specified for the CPU scan
percentage, the display processing time and logic program
processing time will be the same length. The display processing
will not be prioritized.
Setup Procedure
-
In the [System Settings], click [Display Unit].
-
If the [System Settings] tab is not displayed
in the workspace, on the [View (V)] menu, point to [Workspace (W)],
and then click [System Settings (S)].
-
Click the [Logic] tab. In [System Settings], select
[Fixed Scan Time] or [CPU Scan Percentage] and enter a value for
the setting.
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